fax modem

I am using imac, OS version 10.6.8. I could not find a new fax modem at the on line Apple Store. The answer for my question at on-line support was Express Modem Card installation, but I don't think it applies to imac model at all. So, I don't know what's solution for sending and receiving fax in imac computer, if any. I am a PC user, and imac is my first Apple computer. Thanks.